The International Atomic Energy Agency is hosting a meeting in Vienna to discuss plans to enrich Iranian uranium outside Iran, and then ship it back to Tehran. If the talks are successful, they may mark a breakthrough for Iran's controversial nuclear program.

The Vienna talks gather officials from the United States, Russia, France and Iran - along with those from the International Atomic Energy Agency, which is hosting the meeting.

They will discuss a tentative agreement, reached earlier this month in Geneva, for uranium from Iran to be enriched outside that country. The uranium would then be returned to Tehran for use by a small research reactor making medical isotopes.

According to reports, the deal would have Russia taking in partially enriched Iranian uranium for further enrichment. France would then convert the material into metal rods to be used by the Tehran reactor.

The plan follows months of deadlock over Iran's nuclear program and the recent discovery of a previously unknown nuclear-enrichment plant near the Iranian city of Qom.

Speaking at a press conference in Tehran earlier this month, IAEA chief Mohammed ElBaradei said the agency's inspectors would also be visiting the Qom facility on October 25.

"This is a positive development," ElBaradei said. "I have always been of the view that the Iranian nuclear issue is an issue that can only be resolved through dialogue, through diplomacy. I have been saying for a number of years that we need transparency on the part of Iran, we need cooperation on the part of the international community. I see that we are at a critical moment. I see that we are shifting gears, from confrontation into transparency and cooperation."

But observers say there are plenty of unknowns, including whether Iran will cooperate with the tentative deal and to what extent the IAEA will be able to monitor Iran's nuclear efforts.

Tehran claims it is enriching uranium for purely peaceful purposes. Western nations fear Iran is trying to make a nuclear bomb.

Claire Spencer heads Middle East and North Africa programs at Chatham House, in London.

"The idea is to prevent the Iranians from enriching beyond a certain level and anywhere near weaponization," Spencer explained. "But the hitch is now news coming out of Tehran, which suggests they may be actually looking to purchase at more highly enriched levels - up to 20 percent. The threshold for weapons is 90 percent enrichment."

An Iranian official told the Reuters news agency that Tehran would produce the highly enriched uranium at home if the Vienna talks fail.

But Spencer says the discussions could also lead to broader talks with Iran over a host of other subjects, including neighboring Iraq and Afghanistan.

"I think there are many who realize that constantly imposing demands on the Iranians which they either have no intention or the capacity to fulfill for domestic political reasons has not gotten us very far over the last three or four years," Spencer said. "So this could be, certainly it was heralded at the time of the Geneva meeting, as a breakthrough in terms of opening channels more widely with the Iranians."

The U.N. Security Council has imposed three rounds of sanctions on Iran for refusing to stop enriching uranium at home. But Security Council members Russia and China have shown little appetite for another round of sanctions.